In order to accurately prediction of the saturated flow boiling heat transfer coefficients of mixed refrigerants, a heat transfer database containing 3 901 data points was collected from 31 papers, It contains the 11 refrigerants such as the azeotropic refrigerants R507, R513A, the near azeotropic refrigerants R410A, R404A, and the zeotrope refrigerants R407C, R417A, R452A, R448A, R455A, R454C, and R447A. The parameter range of the database covers hydraulic diameters of 0.5~21 mm, saturation pressure of 0.019~2.501 4 MPa, mass flow rate of 50~1 10 9 kg/(m²·s), heat fluxes of 2.5~60 kW/m², qualities of 0.003 6~0.998, and temperature glide of 0.002~10.88 K. The correlations of heat transfer coefficients were collected for 26 pure refrigerants and 16 mixed refrigerants. The existing correlations predicted values were compared with the experimental data, the results showed that the best prediction correlation has a mean absolute error δ_MAD of 37.3% and a mean relative error δ_MRD of-18.3%. Based on the analysis of the existing models, a new heat transfer coefficient correlation was proposed which has δ_{MAD =} 28.8% and δ_MAD = 0.1%, and the prediction performance was significantly improved over the existing correlations.

To identify the key stages and main influencing factors of carbon emissions during the lifecycle of low ambient temperature air source heat pump (chiller) units for industrial and commercial use, and to guide low-carbon design of the units, based on the theory of life cycle assessment, the main greenhouse gas emissions of low ambient temperature air source heat pump (chiller) units for industrial and commercial use were calculated and sensitivity analyzed in five stages:raw material acquisition, processing and assembly, operation, transportation, recovery and disposal. The results show that the main contributions of greenhouse gas emissions during the life cycle of the unit come from the electricity consumption and refrigerant emissions during the operating stage, accounting for over 98%, while other stages can be basically ignored. After replacing R410A with R454B, which has a lower global warming potential (GWP), the total greenhouse gas emissions decreased by 15.14%. When the energy efficiency level of the unit is increased from level 2 to level 1, the total greenhouse gas emissions are reduced by 3.03%. In addition, the change in energy structure has resulted in a reduction of over 6.77% in total greenhouse gas emissions. Therefore, the carbon reduction in the life cycle of low ambient temperature air source heat pump (chiller) units for industrial and commercial use should focus on the operating stage. Using refrigerants with low GWP, improving energy efficiency, and increasing the proportion of new energy in the national energy structure are important ways to reduce carbon emissions throughout the life cycle of the unit.

In order to improve the sealing performance of the triple eccentric all-metal butterfly valve with an integral valve seat structure, the sealing ring single-layer unit of the triple eccentric all-metal butterfly valve was analyzed through a discretization method based on the sealing surface indentation and deformation of the triple eccentric butterfly valve with different structural forms. The stress and deformation were analyzed and calculated, and the sealing structure was improved and verified experimentally. The results showed that when the triple offset butterfly valve was closed, the magnitude and direction of the force acting on each cross-sectional unit of the sealing ring along the flow channel direction were different. At the large end face position, the maximum closing stress acting on the sealing ring cross-sectional unit was 9.145 MPa, and the direction was downward. At the small end face position, the maximum closing stress was 6.482 MPa, and the direction was upward; The optimized metal multi-layer sealing ring has increased the deformation of the sealing ring by 15.4%~27.7% when subjected to the same torque, which is more conducive to forming a sealing zone between the sealing surface of the valve seat and the sealing ring; In addition, by utilizing a specially designed sealing ring structure and assembly process, the metal multi-layer sealing ring can be automatically adjusted, further improving the sealing performance. This enables the triple offset all metal butterfly valve to have both good sealing performance and a long service life. The research can provide reference for the design of high-performance triple eccentric all metal butterfly valves.

To investigate the internal flow mechanism of the electric submersible pump and improve the energy characteristics of the electric submersible pump under gas-liquid two-phase conditions, this paper investigates the effects of different blade opening positions on the hydraulic performance and internal flow field of the electric submersible pump based on the Eulerian-Eulerian non-homogeneous phase flow model with steady numerical simulation. The accuracy of the numerical method is validated by the hydraulic performance test under pure water condition. The effects of different blade opening positions on the internal flow field such as pressure distribution, gas phase distribution and the external characteristics of the electric submersible pump are comparatively analyzed under different flow rate conditions. It is found that changing the opening position will not improve the performance of the electric submersible pump under pure water conditions. However, under the gassy condition, blade opening in the middle and front positions can improve the hydraulic performance of under high flow rate conditions, and the middle opening scheme has the most obvious improvement effect. Under the condition of 5% inlet gas content, the head and efficiency of the middle opening scheme are increased by 0.89m and 3.7% compared with the non-opening scheme. The research results can provide reference for the optimization design of electric submersible pumps.

To address the challenges of high energy consumption and elevated global warming potential (GWP) associated with refrigerants in -86 ℃ ultra-low temperature medical freezers, this study investigates a 568 L freezer employing a single-stage mixed-refrigerant J-T refrigerator. Two ternary hydrocarbon mixtures (R600a/R170/R1150 and R601a/R290/R1150) were experimentally evaluated as environmentally friendly alternatives to the conventional fluoride-containing mixture (R600a/R23/R14/R50). The refrigeration performance of the 2 hydrocarbon blends was analyzed without changing the system components; capillary, compressor and charge adjustments were made for R601a/R290/R1150 with the aim of reducing the refrigeration temperature, compressor discharge temperature and system energy consumption. Experimental results demonstrated that, without system modifications, R600a/R170/R1150 achieved a refrigeration temperature of approximately -60 ℃, whereas R601a/R290/R1150 attained -70 ℃. After reduction of the capillary tube inner diameter and replacement of the compressor with one suitable for R290, R601a/R290/R1150 achieved a refrigeration temperature of -87.3 ℃. Compared to R600a/R23/R14/R50, this configuration reduced the maximum discharge temperature by 11.4 ℃ and energy consumption by 32.9%. However, the pull-down time to -81 ℃ increased from 246 min to 404 min. Further adjustments by increasing compressor speed and refrigerant charge shortened the cooling time to 298 min while reducing energy consumption by 28.9%. These findings confirm that R601a/R290/R1150 not only achieves sub -86 ℃ refrigeration temperatures but also exhibits superior energy efficiency and environmental benefits. Therefore, this hydrocarbon mixture presents a viable eco-friendly alternative for ultra-low temperature freezer applications.

To address the lack of sufficient validation for the thermodynamic design methods of intermediate fluid vaporizers (IFV) and the inadequacy of research on IFV heat transfer testing technologies, a fully structured IFV test prototype was developed. Additionally, an IFV supercritical vaporization heat transfer performance test system was established using liquid nitrogen as the working medium. Laboratory tests on IFV supercritical heat transfer and flow performance were conducted. The results show that the root mean square deviation of gas-phase temperature measurement points in the experimental system is within 1 ℃, and the deviation for liquid-phase measurement points is within 0.1 ℃, demonstrating good temperature uniformity across the measurement points. The thermal balance error of the working medium on both the hot and cold sides is within 5%, indicating that the prototype and testing system are reasonably designed. For IFV boiling heat transfer, the Cooper criterion is found to be overly optimistic under conditions of low wall superheat. Instead, the Mostinsk criterion is recommended, with an additional 10% design margin. The error between the corrected heat transfer coefficient calculations and the experimental measurements is less than 5%. Under experimental conditions, the measured average condensation heat transfer coefficient is approximately 20% lower than the calculated value based on segmented calculations. The causes of weakened condensation in the intermediate medium are analyzed, and improvement suggestions are proposed from the perspectives of structure optimization, heat transfer design and commissioning and installation. This research provides experimental and validation support for the design of IFV supercritical heat transfer systems and serve as a reference for the engineering design of IFV products.

An integrated semiconductor air conditioner for electrical cabinet is designed, and the effects of input current (6~11 A), ambient temperature (20~35 ℃), temperature difference between inside and outside the cabinet (0~40 ℃) and air volume at the hot end on the refrigeration performance of the cabinet semiconductor air conditioner are studied by using the calibrated room calorimeter method. The experimental results indicate that when the ambient temperature is 26 ℃ and the temperature difference between the inside and outside of the box is 20 ℃, the optimal working current of the semiconductor air conditioner is 8 A (36 V), and the refrigeration capacity is the largest (213 W). When the current is 8 A (36 V), with the increase of ambient temperature (20~35 ℃), the cooling capacity and COP increase by 13.9% and 11.9%, respectively. With the increase of temperature difference (0~40 ℃) inside and outside the box, the refrigeration capacity and COP both increase significantly (108~340 W, 0.38~1.21), and the increase of heat exchange capacity is the main reason for the increase of refrigeration capacity. When the air volume of the hot-end fan is increased from 108.63 m³/h to 156 m³/h, the cooling capacity increased by 4.02% and the COP increased by 1.50%. It can provide reference for the design optimization of new cabinet semiconductor air conditioning.

In order to solve gas dynamic noise of Roots vacuum pump due to gas pulsation, return cavity models of four different structures, such as constant rectangular, expanding rectangular, constant depth arc and expanding arc cavities, were designed. The effects of return cavity structure on exhaust pressure, flow rate and internal flow field were analyzed by using the RNG k- εturbulence model and dynamic mesh method, and were verified by experiment. The research results show that the return cavity can increase the pressure of primitives volume in the pump chamber, which effectively suppresses high-pressure gas backflow and improve pressure and flow fluctuation at the outlet. Meanwhile, it can cause lower volumetric flow at inlet. When the inlet pressure is 30~76 kPa, compared with other three return cavities, the fluctuation amplitude of exhaust pressure and flow rate are the lowest at the outlet of constant depth rectangular return cavity (1.31~6.97 kPa and 0.39~1.48 m³/s, respectively). The research results can provide a theoretical basis for noise reduction and structural optimization of the Roots vacuum pump.

In order to improve the phenomenon of piston ring eccentric wear in oil-free lubricated wobble plate compressors, for wobble plate compressors under two typical types of anti-rotation structures, the motion models of the ball hinge on wobble plate and the connecting rod were constructed, and the optimization design method of cylinder distribution radius based on genetic algorithm with the optimization objective of minimizing the average tilting angle of the connecting rod in the motion period was proposed. The study shows that the best distribution circle radius of cylinder is the same for each phase under the bevel gear anti-rotation structure; and the best distribution circle radius corresponding to cylinder in each phase is different for each phase under the roller-straight groove anti-rotation structure, but the mean value can be used as a uniform distribution circle radius, and at this time the effect on the average tilting angle of the connecting rod in each phase is extremely small, less than 5‰; When the tilting angle of the wobble plate is 25° or less, the optimal design values of the cylinder distribution circle radius of the wobble plate compressor under the two types of anti-rotation structures are almost the same. By applying this optimization design method to a variety of existing wobble plate mechanisms, the average tilting angle of the connecting rod is reduced by nearly 21.4%~28.6%, and the peak piston lateral force is reduced by nearly 19.5%~49.6%. This optimization design method can effectively improve the eccentric wear phenomenon of piston ring.

To investigate the influence of a non-parallel rotor blade tip clearance structure on a compressor, this paper studies the effects of different rotor blade tip clearance values on compressor performance and flow field structure and identifies the optimal clearance value. Based on the design clearance value and the optimal clearance value, three expansion clearance distribution schemes were proposed to analyze their effects on compressor performance and flow field structure. The research results indicate that when the rotor tip clearance is set to 0.5τ, the stability margin improvement of the compressor is relatively large, and the performance of the compressor is superior near the stall point. The flow field structure near the stall point is relatively good, and 0.5τ clearance (P2) is considered the optimal clearance value. If the parallel gap distribution is changed to the expansion gap distribution D1, D2 and D3 schemes, the low-energy fluid vortex near the rotor pressure surface is significantly weakened. For the low-speed zone near the trailing edge of the blades, it is further blown away, improving the flow structure and increasing the stall margin. Compared with the baseline scheme, the D1, D2 and D3 schemes improve the stall margin by 1.6%, 1.9% and 2.4%, respectively. The total pressure ratio and efficiency stability margins are improved by 3.18%, 8.56% and 6.20%, respectively. The stability margin improvement rate is increased by 0.59%, 1.45% and 1.55%, respectively. The results provide insights into optimizing the clearance distribution structure for axial flow compressors.